Addition polymers of norbornene having a polar group in its side chain (hereinafter, referred to as a polar group-containing norbornene) are promising as optical films because they have high heat resistance and low double refraction and, further, hydrophilicity, water permeability and adhesion to other materials.
It has been known already that addition polymerization of polar group-containing norbornene is able to be achieved by the use of a cationic organopalladium complex having an organic ligand (allyl or methoxynorbornyl) where carbon atoms participating in the bonding are 3 (Macromolecules, 1996, volume 29, pages 2755 and Acta Polymer, 1997, volume 48, page 385). However, according to such a means, 1/50 to 1/550 equivalent of organopalladium complex is necessary to the polar group-containing norbornene and it is not industrially desirable in view of the manufacturing cost. In addition, the resulting polar group-containing norbornene polymer turns yellow and is not appropriate to be used as an optical film.
In the meanwhile, it has been known that a copolymerizing activity of triethoxysilylnorbornene/butylnorbornen is greatly improved when a cationic allyl palladium complex which is generated by addition of a salt containing a non-coordinate anion to a complex where bulky phosphine ligand and anionic ligand are coordinated to allyl palladium is used as a catalyst (U.S. Pat. No. 6,825,307 B2). However, in this complex, the yield in the polymerization reaction of ethyl norbornenecarboxylate and the yield in the polymerization of norbornene methyl acetate are as low as 0% and 1%, respectively (Polymer Preprints, 2002, volume 43, page 963) and, as such, there are some cases when no effective catalytic action takes place depending upon the type of the polar group-containing norbornene.
On the other hand, there is a description in Papers to be presented at the 85th Spring Meeting of the Chemical Society of Japan, 1PA-019 that a catalytic system where a salt comprising counter-cation and anion having no unshared electron pair in molecules is added to allylcyclopentadienyl palladium is effective for homopolymerization of norbornene. However, there is no description concerning polymerization of polar group-containing norbornene there.
As such, in the already-known catalytic system for addition polymerization of polar group-containing norbornene, there are problems such as that activity of the catalyst is low and that, in some types of polar group-containing norbornene, no polymerization proceeds.
Polymers having a norbornene compound as a main chain have high heat resistance, low double refraction and stability to moisture and, therefore, they are promising as optical films.
In a vinyl polymerization of such a norbornene compound, a production process using a transient metal complex as a catalyst has been particularly receiving public attention in recent years. For example, in Papers to be presented at the 85th Spring Meeting of the Chemical Society of Japan, 1PA-019 and Papers to be presented at the 54th Annual Meeting of the Polymer Society, 1Pe-037, it is mentioned that a catalytic system comprising allylcyclopentadienyl palladium and trityl tetrakis(pentafluorophenyl) borate is effective for homopolymerization of norbornene and for copolymerization of norbornene with methyl norbornenecarboxylate.